1. Field of the Invention
The present invention relates generally to techniques and devices using flip chip bonding. More particularly, the present invention relates metallization schemes.
2. Related Art
Implantable electronic devices provide the potential to improve the quality of life for many patients. For example, devices are currently known which can help to regulate cardiac rhythm, provide automatic defibrillation, and the like. Activities are underway to develop new devices which can directly interface prosthetic devices to the human nervous system. Such devices may enable paraplegics to regain at least partial control of their bladder or limbs, provide vision for the blind, or restore vocal cord function. Promising initial results have already been obtained with some experiments of implanting neural interfaces into patients.
Implantable electronic devices present many challenges such as material compatibilities, identification of complex neural pathways and associated functions, device sizes, among others. The in vivo environment presents liquids and materials which can be quite corrosive to non-native materials. Implanted devices may provoke immune system reactions and cause other problems. Certain materials can aggravate undesired responses to the living organism in which they are implanted. In general, biocompatible materials are those which have the ability to perform with an appropriate host response in a specific application. Implantable electronic devices can use biocompatible materials, but this tends to limit the choices of materials available. For example, lead tends to be toxic and therefore is typically enclosed in a metal container.
It is desirable for implantable electronic devices to be small to minimize trauma caused by insertion and presence of the device, especially in chronic applications. Conventionally, implantable devices are often packaged in a metal enclosure. While the metal enclosure provides an effective barrier between the electronics and the in-vivo environment, considerable bulk and size is added by the metal enclosure. Such an enclosure approach is also impractical, however, for neural interface arrays which require multiple electrical signal interfaces between the electronics and the living body into which it is implanted. For example, U.S. Pat. No. 5,215,088 to Normann et al., which is incorporated herein by reference, discloses a three-dimensional electrode device which can be used as a neural or cortical implant. The device of Norman, also known as the “Utah Electrode Array” can be used to provide a neural interface to electrical equipment for sensing and/or stimulation.
However, these and other approaches still suffer from drawbacks such as large telemetry, material incompatibilities, reliability, among others. As such, devices and methods which facilitate improved telemetry and biocompatibility which are suitable for use in practical applications continue to be sought through ongoing research and development efforts.